Project Planning for Gear Units Efficiency of gear units

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5Project Planning for Gear Units

1 5.1Efficiency of gear units

General information The efficiency of gear units is mainly determined by the gearing and industrial bearing friction.Keep in mind that the starting efficiency of a gear unit is always less than its efficiencyat operating speed. This factor is especially pronounced in the case of helical-worm andSpiroplan

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® right-angle gearmotors.

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R, F, K gear units The efficiency of helical, parallel shaft and helical-bevel gear units varies with the num-ber of gear stages, between 94 % (3-stage) and 98 % (1-stage).

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S and W gear units The gearing in helical-worm and Spiroplan
® gear units produces a high proportion ofsliding friction. As a result, these gear units have higher gearing losses than R, F or Kgear units and thus be less efficient.The efficiency depends on the following factors:•Gear ratio of the helical-worm or Spiroplan

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® stage•Input speed•Gear unit temperatureHelical-worm gear units from SEW-EURODRIVE are winding gear/worm combinationsthat are significantly more efficient than plain worm gear units. The efficiency may reach

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®

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η < 0.5 if the helical-worm or Spiroplan stage has a very high ratio step.

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Self-locking Retrodriving torques on helical-worm or Spiroplan
® gear units produce an efficiency of η ’ = 2 - 1/ η , which is significantly less favorable than the forward efficiency η . The heli-cal-worm or Spiroplan
®

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gear unit is self-locking if the forward efficiency η ≤ 0.5. SomeSpiroplan
® gear units are also dynamically self-locking. Contact SEW-EURODRIVE ifyou wish to make technical use of the braking effect of self-locking characteristics.

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Do not use the self-locking effect of helical-worm and Spiroplan
® gear units as sole safe-ty function for industrial hoist.

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Catalog – DR Gearmotors 01/2008

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